Calcium-magnesium-chloride product and method of making same



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I N VEN TOR TTRN 5 Patented Dec. 3, 1929 i STATES PATENT oFFvlcE WILLIAM It. 'COLLINGS AND .TOI-IN J. SHAIFER, OF MIDLAND, MICHIGAN, ASSIGNORS '.l'O

THE DOW GHEEBIIICAL COMPANY, OF MIDLAND, MICHIGAN, A CORBORATION OF MICHIGAN CALCIUMMAGNESIUMCHLORIDE PRODUCT yAND METHOD 0F MAKING SAME Applicationl lcd March 7, 1928. Serial 110.259,869.

rI'he present improvements relate more particularly to a method-of crystallizing from solutions saturated with hydrated metallic. chlorides, and specifically chlorides of calcium and magnesium, a vproduct containing .such chlorides as'a mechanical mixture of crystals of hydrated chlorides, either single or double or both.

While not necessarily limited thereto, the

,o present improved process finds particularly valuable application in the Working up of the end liquors that result from the treatment of natural brines which, in addition to sodium chloride, contain calcium chloride and magnesium chloride in solution together. As a step in such treatment, the separation of sodium chloride or common salt has long been practiced according toWell known methods, and one approved method for the recovery and separat-ion from. the residual brine of calcium chloride and magnesium chloride, Where thus found present in solution together, is disclosed and claimed in U. S. Letters Patent'No. 1,627,068to A. K. Smith and C.v F. Prutton, dated May 3,1927. However, inall such processes there still remains a residual mother liquor that contains the chlorides in question in varying amounts. Y

One object `of the present improved proccss, accordingly, is to enable theworking up of such end liquor at any stage inthe general process of treating brines of the type in question Where the separation of the individual chlorides is discontinued, Whether for commercial or other reasons.

`A further object is to obtain a product consisting of a mixture of such calcium and magnesium chlorides in the form of a free pouring, non-calzing, granular mechanical mixture of their hydrated chlorides in a Wide range of ratios corresponding to that of the end li uors utilized in the process. This non` ca ing, lfree pouring condition is preferably obtained by superiicially drying such product in accordance with ll. S..Lctters Patent standardizing the content of anhydrous chlorides present in the product at such percentage as maybe desired, e. g., 75 per cent, 80 per cent, etc. Accordingly, although the ratio of the two chlorides in the product may described and particularly pointed out in the claims,.the annexed drawing and the following description setting forth in detail several approved modes of carrying out the process and corresponding modifications in the product obtained, such disclosed modes and products, however, representing but several of the various Ways in which the principle of the invention may be used.

In said annexed drawing Fig. 1 is a diagrammatic representation, somewhat on the order of a iiow sheet, show# ing in proper sequence the principal steps involved in carrying out one form of our improved method or process; and Figs. 2 and 3 are similar flow sheets or diagrams illustrating modifications in such method or process.

Briefly stated, our improved process involves treating a brine containing calcium and magnesium chlorides in any ratio of l. MgCl2 CaCl2 as a mixture of hydrated chlorides in such proportion and composition that in the total analysis of the mixture\and adhering mother liquor so obtained, the molecular ratio ofl MgCl2 08.012

is the same as that in the feed brine, and the salts so obtained may be thereupon dried in a current of hot gases without melting.

Several hydrated chlorides and double chlorides may be separated from MgClgHzO tachydrite, 2MgCl2.CaCl2.12H2O a new compound represented by the formula, MgCl2.2CaCl2.6H2O; and calcium chloride dihydrate, CaCl2.2H2O. By variously combining and proportioning the above mentioned salts, it is possible to obtain a mixture having any desiredl molecular ratio of MgCl2. C3013 When a calcium chloride lnagnesium chloride brine of any analysis is fed to a salting out evaporator operating under any constant vacuum or pressure, water is removed and as a result a solid phase, or phases, Will separate out of solution. If the said solid phase, or phases be continuously removed by a filter and the mother liquor, continuously returned to the evaporator with the feed brine, the analysis ofthe mother liquorin the evaporator will approach and finally approximate a constant analysis. From this point on, the mother liquor analysis in the evaporator does not change substantially, the feed brine merely enters the evaporator, Water is removed as vapor and the balance of the feed is removed as a mixtureof hydrated chlorides and adhering mother liquor. This mixture may then be dried, as by hot air in a dryer, such as a dryer of the rotary kiln or shelf type, to obtain a dried, non-caking free flowing crystalline mixture suitable for applying to roads for dust prevention purposes, or other use.

In general, it is not important just`what hydrates come out as the solid phase in the evaporator, when evaporating brine and returning the -mother liquor separated from the crystals to the evaporator. The chief advantageous characteristis of the crystals, or crystal mixture, so obtained are, easy separation from the mother liquor and capacity for drying by hot gases without melting or balling up. For the above reason, the salting out temperature in the evaporator is best kept low by maintaining a high, vacuum on ther evaporator so as to make the crystal mixture obtained, most easily separable from the mother liquor.

The three figures in the drawing, as stated, illustrate three different modifica-tions of our method, or, more specifically, they show three specific ranges for feed brine composition and evaporator temperature, for each of which the particular hydrated end products thereby obtained are indicated.

Thus, assuming a brine to contain CaCl?, MgCl2, NaCl, and H2O in which the molecular ratio of is less than 2 to 1 C8012 the preferred method of operation is illustrated in Fig. 1 and would be as follows Evaporate the brine under vacuum to a concentration of approximately 40 B. and separate the 40 B. liquor from the salt, which is practically insoluble in this strength liquor. The CaCl2.MgCl2 liquor is then fed to a salting evaporator, operating under high vacuum (say 1 mercury absolute pressure), in which Water is removed as vapor and a thick crystal slurry of easy pumping consistency is obtained. This slurry is then pumped to a rotary suction filter which separates the mother liquor quite completely from the crystals. The crystals from the filter are handled as hereinafter described While the mother liquor is returned to the evaporator along with the feed liquor. After a certain period of operation the mother liquor in the evaporator will reach and lremain ata constant composition of approximately 6% MgCl2, 453% CaCL, and 41% H2O corresponding to a molecular ratio of .132 moles MgCl2 m and 4.77 'moles H2O 1.0 moles CaCl-2 This mother liquor is saturated with tachydrite (2MgCl2.CaCl2.12H2O) and. CaClTQHgO and its saturated boiling point at 1" absolute pressure is approximately 70o C., the evaporator operating temperature in this case.

' The rst crystals obtained when starting up the process as described will not contain a MgCl2 C3012 feed liquor, unless the feed liquor happens to CaCl, librium mother liquor in the evaporator. However, after the equilibrium mother liquor concentration has been attained the proportions of CaCl22H2O, 2MgCl2.CaCl2.12H2O, and adhering mother liquor (.132 MgCl2.CaCl2.4.8H2O) coming off the rotary suction filter Will be CaCl2 ratio of which is identical with that of the feed. It is obvious that, if the M C12 CaCl;

molecular ratio of equal to that in the have the same ratio as that of the equisuch as to give a total analysis, the

ratio l in the feed liquor is nearly the same as thatin the equilibrium mother liquor, the proportion of CaCl22H2O or of 2MgCl2.CaCl2.12HgO may be zero, and that the material being re-v inoved by the rotary suction lter will consist of one of the above named hydrates and the adhering mother liquor in such proportion as to give a total analysis of identical MgCl2 ma@ with that of the feed* liquori .after equilibrium conditions have been at-l tained they may be Imaintained as in .customary manner by suitably controlling the heat iii-put to the evaporator or the rate of feed or both.

'llhe damp crystals obtained from the rotary suction filter are then dried preferably in a current of hot gases in a rotary dryer to dry up the adhering mother liquor and surface dry thecrystals to give a free flowing prac` tically non-caking product.

lin the modified method illustrated in Fig. 2, the ratio of magnesium chloride to calcium chloride in the feed brine may range from 2.00 to 0.50 and in such case, if the evaporation grasses producing a product having the same 08,012.

4ratio as that of the feed. Thus in soine casesk a feed brine of a given analysis may be v 03.1012 ratio by two different ways, that is by salt-ing out two combinations of different hydrated chlorides. These various possibilities, ,together with one set of operating conditions suitable for working up any (MG12-dwg@2 brine, are given in summary form in the following table which shows the general feed worked up to a product` of the saine composition ranges, temperature ranges, components of product, and specific temperature,

pressure and equilibrium mother liquor com position therefore, for one mode of'working the process 1n all feed ranges,vv1z`:

Sample approximate operating Approx. conditions operable 1 .i railige pf m0 GCU al' Solid phases saitng out i. e. components of product; am MgCl; geiglllrne i b 1 t is i r l CaCl, A so u e mother liquor in feed to Temp' Dressur composition eva inches hg. 1 M C] porator mo es g z moles CaCl:

2MgClaCaChl2HrO plus CaCh.2H;0` previously described t'o 1% gglov 70 C. 1 e 2 .5 i .245 Mgonzoaonsnio plus 2Mgc1..oaci,.12n,o T t0 T l ggf 120 C. 1o' T,

' .5 0 v l .03S Mgolizcacnerno plus caoiazmo -1 t0 1-, of 120 o. 12' m be carried on at a temperature from 93 degrees to 152 degrees C., the liquor in the evaporator will become saturated with tachydri'te and with another hydrated double chloride which we believe to benewly discovered by us-in this connection, represented bythe for-l mula MgCl212CaCl2H2O. These two hydrated crystalline salts may be separated out in the same manner as described in connection .with the first method and the resulting prodratio lying between .43 and 0. .Upon carrying out the evaporation of this liquor at :a teinperature between93 degrees and 177 degrees C., the solution in the evaporator becomes saturated with respect to the before men- It may be observed that while according to the process oi U. S. Patent 1,627,068 crystalline double salts of magnesium and calcium are produced for the purpose of increasing thel ratio of the magnesium and calcium t erein, and magnesium chloride, or calcium' chloride is'fnally. separated therefrom as a single'chloride, we produce mixtures of different :double salts or mixtures of different hydrated salts, and then convert these into dried granular or crystalline products containing the mixed chlorides of magnesium and calcium in any desired ratio,

e. g., in that ratio in which they may exist or may be available in theV brine or mother liquor source. Y From the foregoing exemplifcations of the process, it will accordingly be seen that the latter enables the working up of brine ranging from a pure calcium chloride brine to one in which the ratio of magnesium chloride to calcium chloride is as high as 2.00. Correspondingly, the crystalline product obtained will range from calcium chloride dihydrate to a mixture of hydrated salts of the sin le and double chlorides as indicated.

urthermore, the ,product throughout this entire range of chloride mixture, it will be seen, is a mechanical mixture of hydrated single or double chlorides in granular form, which, upon superficial drying, constitutes a free pouring, non-caking, hygroscopie, granular product having very desirable properties. In short, our new process admirably solves the question of how to utilize and work 'up advantageously the mother liquors remaining from the production of pure magnesium chloride and/or pure calcium chloride, or both, from brines or liquors in which such chlorides are present in solution together. The recovery or separation of these pure salts may be carried out to any desired extent without regard to the ratio in which they are left present in the residual solution or mother liquor since the latter by means of the present process may be` converted into the form of the mixed granular hydrated single or double chlorides, or both, as hereinbefore set forth.

The aforesaid hydrated salt mixtures we have found more leasily separated by filtration or draining at all temperature ranges in the `iirst method (Fig. 1) and at the lower temperature ranges in the second method A (Fig. 2.) Indeed they may be even centrifuged without the drawbackof caking to a solid mass and they may be readily separated upon a rotary suctionilter in a continuous manner coriesponding with the approximate rate in which the salts are formed in the evaporator. The process accordino'- 2 b ly, lends itself admirably for continuous operation,` employing an evaporator under reduced pressure and temperature control with .continuous feed, continuous withdrawal of mother liquid and crystals, continuous separation on a lilter with production of a continuous stream of product in moist, granular f orm and a like continuous stream of mother liquor for return to the' evaporator. Moreover, the crystalline product thus separated may,if desired, be dried in a continuous drier.

'In our divisional applications Serial No. 404,528 and Serial No. 404,529, respectively,

filed Nov. 4, 1929, the modifications referred to in Figs. 1 and 3 are more out and claimed;

Other forms o applying the principle of our invention may be employed instead of the ones here explained, change being made in particularly set the 'methodor composition, provided the steps or ingredients stated by any of the following claims or the equivalent of such stated steps or ingredients be employed.

IVe therefore...particularly point out, and distinctly claim as our invention 1. In a method of making a product of the character described, the steps which. consist in adding a solution containing a mixture of hygroscopic metallic chlorides to a mother li uor saturated with respect to one or more o such chlorides, and simultaneously evaporating such moth'er liquid to maintain the same approximately at such point of saturation.

2. In a method of making a product of the character described, the steps which consist in addinga solution containing a mixture of hygroscopic metallic chlorides to a mother liquor saturated with respect to one or more of such chlorides, simultaneously evaporating such mother liquor to maintain the same approximately at such point of saturation, and separating out the crystals of the chloride, or chlorides, thereupon formed.

3. In a method of making a product of the .in adding a solution containing a mixture of hygroscopic metallic chlorides to a mother liquor saturated with respect to one or more ot such chlorides, and simultaneously evaporating such mother liquor to maintain the same approximately at such point of saturation, such evaporation being conducted under controlled temperature and pressure conditions whereby the resultant product has the same chloride composition as that of such added solution.

5. In a method of making a product of the character described, the steps which consist in adding a solution containing a mixture of calcium and magnesium chlorides to a mother liquor saturated with respect to such chlorides, and simultaneously evaporat-ing such mother liquor to maintain the saine approximately at such point of saturation.

6. In a method of making a product of the character described, the steps which consist in adding a solution containing a mixture of calcium and magnesium chlorides to a mother liquor saturated with respect to such chlorides, .simultaneously evaporating such mother liquor to maintain the same ap roxrasa-lea mately at such point ot saturation, separat-- ing out the mixture ot hydrated crystals thereupon formed, and finally superlicially dehydrating such crystals.

d. lin a method ot making a product ot the character described, the steps which consist m in adding a solution containing a mixture el calcium ian'd magnesium chlorides to a mother liquor saturated with respect to such' chlorides, and Vsimultaneously evaporating such mother liquor to maintain the same approximately at such point of saturation, such eyaporation being Aconducted under controlled temperature andpressure conditions whereby the resultant product is ot prede-4 maintain the same approximately at suchr point of saturation, l0. ln a method ot making a product ot the character described, the steps which consist in adding a solution containing a mixture ol calcium and magnesium chlorides to a mother liquor saturated With respect to tachyvdrite and the hydrated double chloride,

MgCl2-2CaGl2ll2U, the molecular ratio ot magnesium chloride to calcium chloride in ,U such added solution not exceeding 2.00, and

simultaneously evaporating such mother liquor to maintain the same approximately at such point ot saturation. l

l1. ln a method of making aproduct ot the character described, the steps which consist in adding a solution containing a mixture ot calcium and magnesium chlorides to a mother liquor saturated with respect to tachv \drite and the hydrated double chloride, ltlglllg-2CaCl2-6H2O, the molecular ratio of magnesium chloride to calcium chloride in such added solutionnot exceeding 2.00 and simultaneously evaporating such mother liluor at a temerature not exceeding 152 whereby such mother liquor is maintained approximately at such point of saturation.

l2. As a new article of manufacture, a free "dowing, non-caking mixture of hydrated crystal chlorides of magnesium and calcium to supercially dehydrated to the point where their tendency to cake together in the package is reduced.J

13. As a new article of manufacture, a free flowing, non-caking mixture of hydrated crystal chlorides of magnesium and calcium,

including the hydrated double chloride, Mgllltlalgllgll, such crystals lacing' superticially dehydrated to the point 'where their tendency to cake together in the paclrc "e y is reduced.

lll. As a new article of manufacture, a tree tlowing, non-caliing mixture of hydrated rides of magnesium and calcium precipitated as crystals ojl tachydrite and the hydr. double chloride MgCl2-2CaCl2ll, a solution saturated with'respect to such. c l rides, such crystals being superticially de drated to the point where their tendens#` cake together in the package is reduced.

l5. 'l'he method of separating calcium and magnesium chlorides from an aqueous tion thereof wherein the molecular ratio or magnesium chloride to calcium chloride lies between 0. and 2.00, which consists in adding such solution to an aqueous solution thereolE that is kept boiling under controlled pressure and temperature conditions, whereby a mian ture ot such chlorides in hydrated torno. a in substantially the same ratio as present in such added solution is caused to crystalliaec l. 'lhe method-'ot separating calcitma and magnesium chlorides from an aqueous solo.m tion thereof wherein the molecular ratio magnesium chloridefto calcium chloride between 0. and 2.00, which consists in adding such solution to an aqueous solution thereot that is kept boiling at a temperature tro-i proximately 42 to 152o C. and con pressure condition, whereby a mixture el chlorides in hydrated form and in sulla, tially the same ratio as present in such aduc solution is caused to crystallize out.

1'?. The method separating calcium and magnesium chlorides from an aqueous solution thereof wherein themolecular ratio ot magnesium chloride to calcium chloride lies between 0. and 2.00, which consists in continuously adding such solution to an aqueous solution thereof that is kept boiling under controlled pressure and temperature conditions, Whereby a mixture ofsuch chlorides in hydrated form and in substantially the same ratio as present in such added solution is caused to crystallize out, and continuously removino' the hydrated chlorides thus formed.

Signed by us, this 1st day of March, 1928.

WILLIAM R. COLLINGS. JOHN J. SHAFER.

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